Water and properties/uses and Aqueous solutions

Question 1

Explain mp, density, and surface tension in relation to water

Answer 1

Melting point (high)
-hydrogen bonds dipole dipole and dispursion
-each molecule can potentially make 4 hydrogen bonds

Density
-decreases when water=solid (more formed hydrogen bonds)
-forms hexagonal shape which cretaes open space between molecules than liquid = less dense

High surface tension
-resistence of a liduid to increase SA
-forces of attraction occur in all directions in water–>no net force
-surface is providing a downward force (no molecules above)
-water has strong hydrogen bonds = high surface tension

Question 2

Structure of water

Answer 2

-polar molecules
-permanent dipole
-main intermolecular force=hydrogen bonding
-high mp and bp
-density
-high surface tension

Question 3

What is capillary action? How does it occur?

Answer 3

Movement of a liquid through/along the surface of another material despite other forces
-cohesive force
-adhesive force
-surface force

Question 4

Define cohesive force

Answer 4

Intermolecular force between same type molecules

Question 5

Define adhesive force

Answer 5

Forces of attraction between unlike molecules

Question 6

Define surface tension

Answer 6

Due to cohesive forces at the surface of material and results in the surface of fluid being under tension
-resistance of a liquid to a change in SA

Question 7

What is a universal solvent? Link to temperature and actions

Answer 7

Pure water
-can dissolve and transport a range of material across the wholeplanet and each cell of a living organism
-from 0-100 degrees usually
-can be a solvent over this temp range

Question 8

Define aqueous solution.

Answer 8

Solutions where the solvent is always water

Question 9

Homogenous vs heterogenous solution

Answer 9

Homogenous
Uniform properties and composition throughout thus solute and solvent are indistinguishable

Heterogenous
No uniform composition and visible distinguishable parts

Question 10

Define dissolution

Answer 10

Dissolving a substance in another

Question 11

Define miscible

Answer 11

Liquids that mix/can be dissolved

Question 12

What is the dissolving process?

Answer 12

1. Forces holding the solute together must be broken
2. Forces holding together solvent must be broken
3. Forces holding solute + solvent together must form

Question 13

What makes a substance soluble?

Answer 13

The solute solvent interactions (or product) must be stronger than the solute solute and solvent solvent interactions.
i.e. like dissolves like-polarity

Question 14

How does water dissolve molecular substances?

Answer 14

-molecule must have sufficient hydrogen bonds in order to dissolve in water
.to make it polar because like dissolves like
-if molecule= large it must have hydrogen bonds across entirety
-if not, it will no fully dissolve

Question 15

Define water dissolving ionic compounds

Answer 15

Process dissolving solid ionic compounds in water and separating the positive and negative ions

Question 16

Explain the attraction of solid ionic compounds in water

Answer 16

Ion-dipole attraction between the ion and corresponding charge of a water molecule
-if the attraction is strong enough water mol. will pull ion from lattice into the solution
-water mols. then surround ion which are then said to be hydrated

Question 17

Explain the process of water dissolving an ion

Answer 17

1. ionic bond is broken in ionic solid
2. hydrogen bonds are broken in water molecule
3. Many ion-dipole attractions formed between ion and water molecules

Question 18

What is a saturated solution?

Answer 18

A solution containing a maximum amount of solute that is able to dissolve
-any more solute added will sit as crystals

Question 19

What is an unsaturated solution?

Answer 19

a solution in which more solute can be dissolved.
-thus will be below the curve

Question 20

What is a super saturated solution?

Answer 20

a solution that contains more than the average solvent that can be dissolved at a given temperature
-above the curve
-unstable

Question 21

Define precipitate?

Answer 21

Insoluble solid products
-usually cloudy/white

Question 22

Define spectator ion

Answer 22

Ion not involved in the reaction

Question 23

Define concentration

Answer 23

Quantity of solute dissolved in a given amount of solution/solvent

Question 24

Define dilute

Answer 24

Small amount of solute dissolved in large volume of solvent

Question 25

Define concentrated

Answer 25

Large solute dissolved in small volume of solvent

Question 26

Equation for Concentration with parts per million (ppm)

Answer 26

conc. ppm = mass of solute (mg) / mass of solution (kg)

Question 27

Equation for Concentration with gram per litre (gL-1)

Answer 27

conc. of solution (gL-1) = mass of solute (g) / volume of solution (L)

Question 28

Equation for Concentration with Mole per Litre (mol L-1)

Answer 28

conc. of solution in mol per litre = mol solute (mol) / volume of solution (L)

Question 29

Define molarity

Answer 29

Measurement of concentration of a solution

Question 30

Relationships between dilution and conc + vol

Answer 30

As the amount of solute stays unchanged, the number of moles of the solute will not change but the conc and volume will